Not palsas. Palsas are formed on bogs, as peat is necessary for summertime insulation. Because all vegetation (if there ever was any)—and with that all the peat—has long since left Mars, any former palsas shouldn't really leave that visible marks.

Palsa formation usually requires not just a peat bog, but also snow cover. Ice lenses are formed underneath the peat layer on spots where winter freezing occurs unusually rapidly e.g. due to a thin spot in snow cover. (Palsas have been deliberately crea

I recall that when Clarke was still alive he noted several geological features which were of personal interest to him, one of which was a "sandworm" type of feature very much like this one.

It's easier to find Clarke's off-the-cuff remark that some features look like banyan trees, but I know he wrote another piece about features other than those. Hive mind, can you please provide the citation that I cannot?

Given that the blurb on the HiRISE page say "but for now this is a mystery," I'm not seeing any evidence of scientists being scared of saying they don't know. In fact, making a high profile general public article highlighting stuff you don't understand seems like the exact opposite of the scientists being scared to point out what you don't know.

Instead of "I don't know" they can just throw massive error bars on the figure. For example, the earth may be 4.5 billion years old +- 20 billion years. (Thats right, it may not be created until the future...)

Try looking at the image slide show on the very page linked in the summary. One of the craters on Mars has tectonic activity where one side of the fault has been uplifted while the other side went down. The fault goes right through the crater showing the activity happened after the impact created the crater.

Looks like the kind of ice and snow that remains on the shadow side of a mountain or ridge. The ice slowly melts, so the water gradually creates a depression on one side and deposits mud at the bottom.

If you figure each put was made by a chunk of ice, which laid on the surface to trap blown debris, then subliminated away, you'd get something like that. The one to the right with ones inside of on pit would have been made by a ice boulder fracturing apart then its parts sublimating away.